JPS5935746B2 - Method and device for controlling machining cycles of machine tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling machining cycles of a machine tool on a workpiece including a tool and a movable tool feed.

Stock of workpieces being machined (StOck)
High-power (per hour) grinding machines are known in which the grinding wheel transport speed is controlled continuously or stepwise on the basis of measured values of .

It is also well known to continuously and adaptively vary the feed rate according to machine characteristics such as the actual stock removal rate or the pressure between the grinding wheel and the workpiece. The purpose of these adaptive controls is to improve the process of machining the workpiece. However, these known grinding machines have several drawbacks. For example, the feedback system does not operate accurately and sensitively when there is less stock to be removed, resulting in shorter cycles. Furthermore, precise feedback systems are highly complex, non-adaptive, and difficult to understand structures. It is an object of the present invention to provide a control method and device that is advantageous in terms of rapid response, accuracy, stability, adaptability and cost.

In order to achieve the above object, the control method according to the present invention measures the workpiece during machining in order to generate a signal depending on the size of the workpiece, and at least at the last stage of each machining process, the control method according to the present invention continuously programming the feed rate of the tool feed as a function of the measured dimensions of the workpiece to obtain a first feed rate control signal, referenced to the position of the tool feed during unloading of the workpiece; Generates a signal according to the position of the tool feeder, compares the signals according to the size of the workpiece and the position of the tool feeder, and determines the size of the workpiece and the tool as a result of the tool thrust during machining. obtaining a signal responsive to strain caused by a series of moving bodies including a second
obtain a feedrate control signal of the first feedrate control signal and combine the first and second feedrate control signals to vary the first feedrate control signal, particularly when the distortion decreases below a preset value; The first feed rate control signal, ie, increases the feed rate.

Furthermore, the leg restraint device according to the present invention includes a measuring device that measures the size of a workpiece being machined, a power device that includes a motor that drives a tool feeder, and a signal that outputs a signal that displays the position of the tool feeder. and a zero setting device that resets the position responsive device when finishing the workpiece, the position of the tool feeder is adjusted to the position of the tool feeder based on the position of the tool feeder when finishing the workpiece. a programming device connected to the measuring device and the power device and programming the feed rate of the tool carriage according to the measured dimensions of the workpiece at least at the last stage during each machining operation; and a comparator device connected to the position responsive device and the measuring device to produce an output signal responsive to the strain produced by the series of moving bodies, including the workpiece and the tool, as a result of tool thrust during machining. , connected to the comparison device and the programming device, for changing the programmed speed of the tool feed according to the output signal, and in particular changing the programmed speed when the strain decreases below a preset value. Equipped with an increasing control device.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, a ring 3 resting on wheel chocks 4, 5 is rotated by an axis (not shown) and is grounded on its outer surface by a grinding wheel 6 of a high-power grinding machine. The grinding wheel 6 is mounted on a movable tool feed T on a base 8. The tool feed T is moved by a stepper motor 10 to which is functionally connected by dotted line 9 as shown. The step motor 10 is connected to a screw precision device (not shown) Vc. Yotsute movement<. The ring is measured by an electronic instrument 11 with movable arms 12, 13 and a position transducer (not shown). Instrument 11 is connected to sense amplifier 14 and sense amplifier 1
4 outputs an analog voltage proportional to the stock of the ring 3, that is, the difference between the target outer diameter and the actual outer diameter at the end of machining.

Output terminal IT of device 14 is connected to programming unit 18 via contacts 16 of relay 19. The program unit 18 outputs a continuously variable voltage in response to its input signal, as described below, and is connected to one input of the adder 21. The output of the adder 21 is the step motor 10.
It is connected to the power supply circuit 22 of. The circuit 22 has a voltage-to-frequency converter that outputs a pulse with a frequency proportional to the analog input quantity, which causes the rotor of the motor 10 to advance to the next step and the tool carriage T to operate accordingly. do. The digital counter 23 is connected to the motor 10 and the circuit 22
connected to the rotor to count the number of rotor steps.

Counter 23 has a reset terminal 25, which is connected to the output of comparator 2T. The two inputs of the comparator 2T are respectively connected to the output of the device 14 and to a potentiometer 29 which produces an adjustable reference voltage. The output of the counter 23 is connected to a digital-to-analog converter 31, and the converter 31 is connected to an adapter 33. The output of the adapter 33 is connected to a terminal 35 of the relay 19 corresponding to the instant 16, to one input terminal of the comparator 3T and to the negative input terminal of the differential amplifier 39, respectively. The other input of comparator 31 and differential amplifier 39 are both connected to the output of device 14. The output of comparator 3T is connected to winding 41 of relay 19.

A contact 43 is provided in series with the output of the differential amplifier 39.
The contact 43 is opened and closed by an excitation winding 45, and the winding 45 is connected in series with the output of a comparator 46, whose two inputs are connected to the output of the device 14 and the adjustable It is connected to a potentiometer 4T that generates a reference voltage. The output of the differential amplifier 39 is transmitted via the contact 43 to
Arithmetic processing device 5 that controls the input of the program unit 51, one input of the comparator 53, and the mounting of the grinding wheel 6.
connected to one input of 5. The relationship between the input voltage Vi' and the output voltage Vu' of the unit 51 is shown in FIG. The output of unit 51 is connected to the second input of adder 21. A second input of comparator 53 receives an adjustable reference voltage via potentiometer 5T, and the output of comparator 53 is connected to outlet terminal 59 of processing unit 55.
The grinding machine further has a control display device 65 for controlling the different stages of the machining cycle, the device 65 including a comparator 2.
The output of T, the arithmetic processing unit 55 and the comparator 3T are connected.

The grinding machine operates as follows.

When the diameter of the ring 3 produced by the grinding wheel 6 decreases to a set value, the output signal of the device 14 causes the output of the comparator 2T to be reversed.

The output signal of the comparator 2T sets the counter 23 to zero and controls the device 65 to begin the post-machining operation of the machining cycle. This operation includes 1 stopping the electric motor 10, 2 reversing operation to return the tool feeder T, and 3 moving the ring 3 to the carrier (
(not shown), and the operation of removing the finished ring and installing the newly ground ring (obviously, this is done by the loading and unloading arms). 5) and return the meter 11 to the measuring position.
Due to the operation of the device 65 connected to the power supply circuit 22,
When the electric motor 10 starts from a stationary stage and rotates at maximum speed in order to return the tool carriage T to its original position, the tool carriage T returns a predetermined distance and the counter 23 indicates that before the ring 3 is ground. The motor 10 is set based on the maximum diameter of the motor 10.
The number of steps is counted up to a predetermined value. The electric motor 10 then comes to rest and reverses its direction of rotation, guiding the grinding wheel 6 into the ring 3 already installed in the loading phase.
When the grinding wheel 6 moves in the direction of the ring 3, the contacts 16 close the terminals 35 (relay 19 is de-energized) and the approach speed is determined as follows. The output digital signal of the counter 23 is converted into an analog signal by a converter 31.

The output signal of the converter 31 is indicative of the position of the tool carriage T. The grinding wheel 6 operates so that the stock of the ring 3 is reduced. When the diameter of each ring 3 reaches the desired value, the counter 23 is set to the atmosphere, so the tool feed table T returns a predetermined distance. In this way, the wear and tear of the grinding wheel 6 is compensated for (so that the position of the tool carriage T can be changed at the end of its separation from the ring 3). The forward feed value L of the grinding wheel, which corresponds to the theoretical reduction in the diameter of the ring 3, if the grinding wheel is in contact with the ring and neglecting the kinematic chain between the workpiece and the grinding wheel, is 6, the shape of the ring 3 and the relative position of these axes and the type of grinding machine will vary between the values L and 2L. The adapter 33 thereby converts the signal regarding the displacement of the tool carriage T into an imaginary change in the carriage.

This change is fictitious. That is, grinding wheel 6
is not in a position to be in contact with the ring 3, and furthermore, when said contact is made, the above-mentioned relationship is not necessarily constant during the finishing period by the same machine due to the aforementioned tension, changes in the grinding wheel during grinding, and other factors. be. However, before the grinding wheel 6 approaches and contacts the ring 3, the adapter 33
The difference between the output signal of and the initial diameter of ring 3 (measured by instrument 11) indicates the distance traveled by tool carriage T. During this approach, the speed of the tool carriage T is set to the program unit 1.
8, this unit 18 receives at its input the signal Vi provided by the adapter 33, and the second
A signal Vu with an amplitude varying according to curve "a" in the figure
emits. During this approach, contact 43 is open;
The program unit 51 emits an output signal Vu' having a constant amplitude equal to the maximum value VO of the curve "d" of FIG. 5.The adder 21 receives the signals Vu and Vu' and adds them, It emits an output signal that changes according to the dashed line indicated by ``b''. Therefore, the step motor 10 controls the forward movement of the tool carriage T. When the grinding wheel 6 contacts the ring 3, the output of the comparator 3T is reversed, thus providing a control signal to terminate the gap removal. This signal is fed back to the comparator 3T before and after contact. device 14
is readily obtained by subtracting or adding an appropriate correction signal from the output signal of .

As is clear from the curve "b" in FIG. 2, the feed rate in the approach phase decreases slowly until the grinding wheel 6 contacts the ring 3, and a stepwise decrease occurs at the contact T. In fact, the comparator By inverting the output of 3T, winding 4
1 is energized, contact 16 opens terminal 35 and closes terminal IT. From the time T, the output signal Vu of the unit 18 varies according to the curve c'' of FIG. Circuit 22 receives a signal corresponding to curve "b" in FIG. 2 to drive motor 10.
The grinding wheel 6 takes stock away from the ring 3.

When ring 3 reaches a predetermined stock value, the output of device 14 becomes equal to the value given by potentiometer 4T and the output of comparator 46 is reversed, winding 45 is energized and contacts 43 are closed. (time T2 in FIG. 2). The output voltage of the differential amplifier 39 corresponds to the elastic strain received from the series of moving bodies consisting of the ring 3 and the grinding wheel 6, and is based on the thrust of the grinding wheel 6. In fact, this voltage corresponds to the difference between the stock in ring 3 and the hypothetical stock mentioned above.
Strictly speaking, this voltage represents the increase in strain relative to the total strain when the link 3 reaches its target diameter. By closing the contact 43, a tension signal is sent to the programming unit 51, from which an output signal Vu is emitted by the input signal Vi' according to the curve d'' in FIG. Voltage (that is, no output voltage at all) corresponds to strong tension, and conversely, strong tension corresponds to low output voltage.From time T2, which corresponds to the closing of contact 43, the output signal of adder 21 changes according to the dotted line "e" in FIG.

After time T2, a signal Vu corresponding to the curve "c" and a change signal Vu' corresponding to the curve "d" are calculated. In this way, if excessive tension is detected, the step motor 1
0 is significantly slowed down and the tension is reduced. The machining continues with tension-based control, and at time T3 the instrument 11 detects that the target diameter has been reached from the ring 3. The control from time T2 to time T3 is adaptive control for distortion.

The speed of electric motor 10 is determined by programming units 18 and 51.
The sum of the output signals Vu and Vu' is Vu+Vu'. The output signal Vu' of the program unit 51 changes as a function of the signal Vi6 corresponding to the generated distortion, as shown in FIG. If the distortion is large at time T2, the signal Vi
If ' is greater than the value Vi, the output signal Vu' will be zero. This means that the feed rate is determined solely by the output signal Vu of the program unit 18. Therefore, the feed rate is lower and the distortion is also reduced. Then the signal Vi
When Vu' also becomes low and becomes smaller than the value Vi', the output signal Vu' takes a positive value according to the curve Wd'. When the output signal Vu' takes a positive value, the total control signal Vu+Vu' increases and the feed rate increases. As the feed rate increases, the strain increases;
Conversely, the output signal Vu' decreases according to the curve "d". In this way, the feed rate is adaptively controlled so that the strain is neither too high nor too low. The strain is not too low. The purpose of this control is to prevent the machining time from becoming too long.This adaptive control is continued until time T3, at which time the instrument 11 detects that the ring 3 has reached the target diameter. Then, the output signal of the comparator 2T is inverted by the output signal of the device 14.The output signal of the comparator 2T sets the counter 23 to the atmosphere and the device 65 starts the post-machining operation of the machining cycle. This operation includes 1 stopping the electric motor 10, 2 reversing operation to return the tool feeder T, 3 removing the instrument 11 attached to the carrier (not shown) from the ring 3, and 4 finishing the The act of removing the ivy ring and installing the newly ground ring {obviously, this is a loading process.
arm and unloading arm),
5 This is an operation to return the meter 11 to the measurement position. In this embodiment, the above-mentioned adaptive control is performed at the final stage of machining, so it meets the demands for productivity improvement such as short machining time, the demand for control stability, and the improvement of workpiece machining accuracy. It is possible to realize both the requirements of

This adaptive control can also be done in different ways, for example as shown in FIG.

In the apparatus shown in FIG.
A differential programming unit 68 which can be replaced by another programming unit 68 connected to the device 14 as shown and a differential amplifier 69 whose inputs are connected to the outputs of the programming unit 68 and the differential amplifier 39 is Based on the stock measured from the machined ring 3, a signal corresponding to the appropriate tension is generated.

This signal is compared with a signal corresponding to the actual tension in a differential amplifier 69. and provides signals for correction of the controlled feed rate provided by program unit 18. It is also possible to disconnect the program unit 18 after the time T2 when the contact 43 is closed and continue machining by means of the output signal of the program unit 51 which supplies a different program. As another variation,
While the programming unit 18 remains connected, the connection of the programming unit 51 can be controlled only when the measured tension value exceeds a predetermined value (after a predetermined stock has been reached).

This variant is achieved by using a comparator 53 which receives a tension signal at one of its inputs (after the contact 43 has been closed) and compares this signal with a reference signal provided by the potentiometer 5T. It will be realized. However, the first
In the device shown, the comparator 53 is used for a different purpose, more precisely to supply a consent signal to a processing unit 55 which controls the machining by the grinding wheel 6. The processing unit 55 is, for example, disclosed in Italian Patent No. 960,035.
can be made based on the description of This patented invention discloses a method and apparatus for checking capacity deficiencies in a grinding wheel of a grinding machine. According to this patent, the inspection is carried out by detecting signals due to capacity deficiencies in the grinding wheels (e.g. stock removal rate or time required to remove a given amount of stock) to determine the predetermined value of the machine finishing cycle for each stroke. This signal is compared with a predetermined value to obtain an error signal, which is integrated in a subsequent step.
The circuit shown in this patent, with some modifications, is used to integrate an error signal as a function of the deviation of the actual tension from a predetermined tension due to a series of moving bodies of the grinding wheel segment. A circuit diagram of an embodiment of the program unit 18 is shown in FIG.

The input terminal TO of the unit 18 is connected to an inverter T1 and a resistor T2.
is connected to the negative input of the operational amplifier T4, and the positive input of the amplifier T4 is grounded through the resistor T5. Three circuits are connected in parallel between the output of amplifier T4 and its negative input. The first circuit consists of a resistor TT, the second circuit consists of a diode T9 and a resistor 80 connected in series with it, and the third circuit consists of two diodes 82.
83 and a resistor 85 are connected in series.

Resistor 85 is short-circuited by contact 8T. The contact 8T is mechanically interlocked with the contact 16 as shown by the dotted line 89,
When contact 16 closes terminal IT, contact 8T also closes. Conversely, when contact 16 closes terminal 35, contact 8T opens. Points A and B in FIG. 2 are the threshold value of diode T9 and the two diodes 82 and 83, respectively.
corresponds to the threshold of

Program unit 51 is implemented as shown in FIG. A negative input of the operational amplifier 93 is connected via a resistor 94 to a terminal 95 to which a constant voltage -VO is applied. This negative input terminal is also connected via a resistor 9T and a contact 43 to a terminal 98 that constitutes the output of the differential amplifier. Augmentator 93
A diode 99 is connected between the negative input and output of the .
Another diode 100 is connected in series with the output of the amplifier 93, and the cathode of the diode 100 is connected to the negative input of the amplifier 93 via a resistor 101. In FIG. 5, when the voltage value Vi' is equal to the atmosphere (no tension) or when the contact 43 is opened, the output voltage Vu' becomes equal to the value VJ.

When the contact 43 is closed and the value Vi' is intermediate between the atmosphere and Vi,', the effect of Vi' is opposite to the effect of VO, and the output voltage VJ is equal to the point Vi' on the abscissa and the point VO on the ordinate. varies according to the division enclosed by. If the input voltage is equal to or greater than Vi,', the value of the output voltage VLl' is equal to
The speed of FIG. 1 is determined solely by the program unit 18. Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the present invention.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the device that controls the machining cycle of a high-power grinder, Figure 2 is an explanatory diagram showing the operating process of the device in Figure 1, and Figures 3 and 4 are the programs in Figure 1. 5 is an explanatory diagram showing the operation of the program unit shown in FIG. 4, and FIG. 6 is a block diagram showing a modification of the apparatus shown in FIG. 1. 3...Ring, 4, 5...Wheel stopper, 6
...Grinding wheel, T...Tool feed stand, 8
...Base, 10...Step motor,
11... Instrument, 12, 13... Movable arm, 14... Detection amplifier, 16...
Contact, 1T...Terminal, 18...Program unit, 19...Relay, 21...
...Adder, 22...Power supply circuit, 23...
... Counter, 25 ... Reset terminal, 2T
... Comparator, 29 ... Potentiometer, 31 ... D-A converter, 33 ...
Adapter, 35...Terminal, 3T...Comparator, 39...Differential amplifier, 41...
Winding, 43... Contact, 45... Excitation winding, 46... Comparator, 4T... Potentiometer, 51...・Program unit, 5
3... Comparator, 55... Arithmetic processing unit, 5T... Potentiometer, 59...
・Terminal, 65... Control display device, 68...
...Program unit, 69...Differential amplifier, TO...Terminal, T11...Inverter,
T2...Resistor, T4... Arithmetic amplifier,
T5, TT, 8O, 85...Resistance, T9, 82
, 83... Diode, 8T... Contact, 93... Operational amplifier, 94... Resistor, 98... Terminal, 99, 100 ······diode.

Claims (1)

[Claims] 1. Measuring the workpiece during machining to generate a signal depending on the size of the workpiece, at least at the last stage of each machining process as a function of the measured dimensions of the workpiece. Continuously programming the feed rate of the tool feed to obtain a first feed rate control signal, the signal being responsive to the position of the tool feed relative to the position of the tool feed during finishing of the workpiece. occurs,
The signals are compared depending on the size of the workpiece and the position of the tool feedstock, respectively, to respond to the strain caused by a series of moving bodies, including the workpiece and the tool, as a result of the tool thrust during machining. obtaining a signal and continuously programming a feed rate of the tool carriage as a function of the signal responsive to the strain to obtain a second feed rate control signal and combining the first and second feed rate control signals; a tool and a movable tool carriage for changing the first feedrate control signal, increasing the first feedrate control signal, i.e. the feedrate, especially if the strain has decreased below a preset value; A method for controlling the machining cycle of a machine tool for a workpiece containing 2 Displays the measuring devices 11 and 14 that measure the size of the workpiece 3 during machining, the power units 9, 10, and 22 including the motor 10 that drives the tool feeder 7, and the position of the tool feeder 7 position response devices 23, 31, 33 that output signals to
and the position response devices 23, 31, when finishing the workpiece.
33, and outputs a signal according to the position of the tool feed stand 7 with reference to the position of the tool feed stand at the time of finishing the workpiece; The measuring devices 11, 14 and the power devices 9, 10, 22
a programming device 18 connected to and for programming the feed rate of the tool carriage 7 according to the measured dimensions of the workpiece 3 at least at the last stage during each machining; The workpiece 3 is connected to the measuring devices 11, 14 as a result of the thrust of the tool 6 during machining.
and a comparator 39 which produces an output signal in response to the strain caused by a series of moving objects including the tool 6, which is connected to the comparator 39 and the program device 18, and which is connected to the program device 18 to adjust the tool carriage 7 according to the output signal. A control device 21 for varying the programmed speed and increasing this programmed speed, especially if said distortion has decreased below a preset value.
, 51, and controls a machining cycle of a machine tool for a workpiece 3 including a tool 6 and a movable tool feeder 7.